On Mauginiella scaettae

Transcription

1 On Mauginiella scaettae J. A. von ARX Centraalbureau voor Schimmelcultures, Baarn, Holland J. P. van der WALT & N. V. D. W. LIEBENBERG Microbiology Research Group, Council for Scientific and Industrial Research, Pretoria Abstract. TEM micrographs show that Mauginiella scaettae CAV. has cell walls and septa characteristic of Ascomycetes. The fungus may be related to Monilia. Some other genera with arthroconidia, earlier placed in synonymy with Mauginiella, are discussed. Introduction Mauginiella scaettae CAV. causes a severe date palm disease in North Africa and the Middle East (RATTAN & AI-DBOON, 1980), rotting the spadix and inflorescence. The fungus was first described by CAVAKA (1925) from Cyrenaica (Libya). The name has been chosen in honour of Dr. A. MAUGINI and Dr. H. SCABTTA, at that time working at the "Istituto Agricola Coloniale Italiano". MAIRE & WERNER (1937) rediscovered the species in Morocco and renamed it Geotrichum Fig. 1. Mauginiella scaettae: camera lucida drawings of conidiogenous structures 42

2 Fig. 2. (CBS ) & 3. (CBS ) Mauginiella scaettae: TEM micrographs of septate hyphae from cultures grown on YM agar for 4 days at 28 C, fixed in 5% glutaraldehyde, post fixed with 1% osmium tetroxide and stained with uranyl acetate and Reynolds lead citrate. Note the ascomycetous type of cellwall consisting of a rather thin dark outer layor and a broader lighter inner layer. The bar represents 0.5 micron

3

4 scaettae (CAVARA) MAIRE. CIFERRI (1958) incorrectly considered it to be identical with Sporendonema epizoum (COEDA) CIFEEBI & REDAELLI (= Wallemia sebi (FR.) V. AEX). Full descriptions of the fungus and the disease have been given by GOIDÄNICH (1937), AL-Asiet al. (1971), NICOT (1972) and SIGLER & CAEMICHAEL (1976). CARMICHAEL et al. (1980) suggested that the genus is comparable to Moniliophthora EVANS et al. (1978). However, the affinity of Mauginiella to either the Ascomycetes, Basidiomycetes or Endomycetes (Dipodascaceae) has remained doubtful. Description The CBS fungus collection has three strains of Manginiella scaettae, all isolated from Phoenix dactylifera. CBS was received from J. CHEESTIAN, CBS from J. SCHREURS. The following description is based on the most recent culture, CBS , isolated by R. KENNETH (Israel) from a spadix of the date palm in 1973: Colonies on malt agar at 25 C with a daily growth rate of mm, white, lanose due to aerial hyphae and conidiogenous cells; aerial hyphae 3-4 \im broad, regularly septate; immersed hyphae repeatedly branched, y.m broad; conidiogenous hyphae develop as lateral branches of aerial hyphae, occasionally (mainly in fresh isolates) in sporodochial tufts, are more or less erect, simple or with some branches, variable in lenght, 5 9 yua broad, become many-septate and disarticulate into arthroconidia; arthroconidia 1-, 2- or up to 6-celled, cylindrical or ellipsoidal, hyaline, 9 40x5 9 [xm; with slightly conical or rounded ends, marginal rings of dehiscence and apical disjunctive tips; single cells 7 12 [i,m long, often swollen (Fig. 1). TEM micrographs were made from ultrathin sections of aerial hyphae of CBS and CBS They show a rather thick cell wall with a thin, electron-opaque outer layer and a broader, translucid inner layer. The cross wall has a rather wide central pore which may be occluded with or surrounded by dark globules (WORONIN bodies, Kg. 2). None of the strains of Mauginiella scaettae is coloured with Diazonium Blue B salt in petri dish cultures on malt extract agar (van der WALT & HOPSU-HAVTJ, Conclusions The ultrastructure of the cell wall and hyphal septa and the Diazonium Blue B test show that Mauginiella scaettae represents an anamorph of an unknown ascomycete. The genus Geotrichum LINK is unrelated, has septa with numerous micropores (plasmodesmata) (e. g. COLE, 1975; COLE & SAMSON, 1979), represents anamorphs of 43

5 Dipodascus LAGERH. and should be classified in the Endomycetes (von ABX, 1981). Moniliophthora roreri (CIFERRI) EVANS et al. (= Monilia roreri CIFERRI) is also unrelated having septa with dolipores which indicate a basidiomycetous affinity (EVANS et al., 1978). This fungus is the causal agent of (frosty) pod rot of cocoa in South America, and in culture the colonies are much more restricted than those of Mauginiella scaettae. Wallemia sebi also has septa with dolipores (TERRACINA, 1974; COLE & SAMSON, 1979), is highly osmophilic and forms red-brown restricted colonies on sugar-rich media. The genera Trichosporonoides HASKINS & SPENCER and Moniliella STOLK & DAKIN also form arthroconidia, have septa with dolipores (HASKINS, 1975; MARTINEZ, 1979) and are considered to be of basidiomycetous affinity. The two genera arc close to each other and the ability to ferment sugars and to assimilate fatty compounds and other hydrocarbons distinguish them from other Basidiomycetes. These characters are also combined in a few Endomycetes (yeasts), e. g. Yarrowia lipolytica (WICKERHAM et al.) van der WALT & v. ARX, the teleomorph of Candida lypotytica (HARRISON) DIDDENS & LODDER. The characteristic species of the genus Trichosporon are morphologically similar to Moniliella, but show no fermentation and are not lipolytic. The genus Mauginiella probably is close to Monilia PEBS. The conidiogenesis is rather similar and the typical species of the latter genus also causes inflorescence decay (blossom blight). The genus Monilia differs from Mauginiella by having regularly constricted conidiogenous hyphae, 1-celled, usually barrel-shaped conidia with more distinct disjunctive structures and by the formation of dark stromata or pseudosclerotia, which may give rise to the Monilinia telemorph following a resting period. References AL-ANI, H. Y. et al. (1971). Reaction of date palm cultivars to inflorescence rot and persistency and spreading of the disease. Phytopath. Medit. 10: (and 82 85). ABX, J. A. von (1981). The genera of fungi sporulating in pure culture. 3rd edition, J. Cramer, Braunschweig, 424 pp. CARMICHAEL, J. W., KENDRICK, W. B., CONNERS, I. L. & SIGLER, L. (1980). Genera of Hyphomycetes. Univ. Alberta Press, Edmonton, 386 pp. CAVARA, F., 1924 (1925). Atrofia florale in Phoenix dactylifera di Cirenaica. Rend. R. Accad. Naz. Lincei, ser. 6, CIFERRI, R. (1958). Mauginiella, a synonim of Sporendonema. Atti Ist. Bot. Lab. Critt. Univ. Pavia, ser. 5, 15: COLE, G. T. (1975). The thallic mode of conidiogenesis in the Fungi Imperfecti. Can. J. Bot. 53: & SAMSON, R. A. (1979). Patters of development in conidial fungi. Pitman, London, 190 pp. 44

6 EVANS, H. C, STALPBBS, J. A., SAMSON, R. A. & BENNY, G. L. (1978). On the taxonomy of Monilia roreri, a pathogen of Theobroma cacao. Can. J. Bot. 56: GOIDÄNICH, G. (1937). II marciume dell'infiorescenza della palma da dattero causata da Alauginiella scaettae. Agric. Colonials 31, 10: 3 9. HASKINS, R. H. (1975). Septal ultrastructure and hyphal branching in Trichosporonoides oedocephalis. Can. J. Bot. 53: MAIEE, R. & WERNER, R. G. (1937). Fungi Maroccani. Mem. Sc. Nat. Maroc 45: MARTINEZ, A. T. (1979). Ultrastruoturo of Moniliella, Trichosporonoides and Hyalodendron. Stud. Mycol. Baarn 19: NICOT, J. (1972). Mauginietta scaettae. Fiches Phytopath. Trop. no. 24, 6 pp. (Suppl. Rev. Mycol. 37). RATTAN, S. S. & AL-DBOON, A. H. A. (1980). Notes on fungi associated with Date-Palm. I. Sydowia 32: SIGLBB, L. & CARMICHAEL, J. W. (1976). Taxonomy of Malbranchea and some other Hyphomycetes with arthroconidia. Mycotaxon 4: TERBACINA, F. C. (1974). Fine structure of the septum in Wallemia sebi. Can. J. Bot. 52: WALT, J. W. van der & HOPSU-HAVU, V. K. (1976). A color reaction for the differentiation of ascomycetous and hemibasidiomycetous yeasts. Antonie van Leeuwenhoek 42: